The structure and mechanisms of formation of the age related fluorescent moieties in human lens proteins will be investigated at the molecular level. Young human lenses and calf lens protein will be irradiated with near UV light under physiological conditions. The impact of physiological and nonphysiological sensitizers and free radical quenchers will also be examined. The resulting photolyzed protein will first be compared to human cataractous lens protein on the basis of fluorescence, amino acid composition and aggregative properties. Both the irradiated protein and cataractous lens protein will then be proteolytically digested and the fluorescent moieties isolated by biochemical separation techniques and high pressure liquid chromatography. Comparisons between the fluorescent compounds from in vivo and in vitro sources will then be made on the basis of natural product techniques (ultraviolet, infra red, nuclear magnetic resonance and mass spectrometry). By these means the extent to which photochemical reactions are involved in the age related molecular changes in human lens protein will be unambiguously determined.